Overtone spectrum of SiH stretching in H2SiCl2
Chin. Phys. B, 2005, 14 (3):
The overtone spectra of H2SiCl2 molecule in the regions of 2000—9000cm-1 and 12000—12900cm-1 at room temperatures have been studied by use of high-resolution Fourier transform spectroscopy and sensitive-intracavity-laser absorption spectroscopy, respectively. The variations of vibrational quantum numbers ΔVSiH=1, 2, 3, 4 and 6 for the overtones of the SiH stretching have been analysed and assigned with the local mode model and the normal mode model. The values of harmonic frequency ωm, anharmonicity constant χm, bond coupling constant λ, the Morse oscillator parameters De, α, and interaction force constant frr′ are derived from the experimental spectrum with nonlinear least-squares fitting. The most striking feature of the SiH2Cl2 is that the larger the vibrational energy, the smaller the energy difference between a couple of lowest stretching states of a given manifold, and finally, the couple of lowest stretching states are degenerated within the experimental error for ΔVSiH≥4 vibrational manifolds. The degenerate energy level structure resembles that of a diatomic Morse oscillator; the transition energies show a remarkable fit to the Birge—Sponer relation. The high vibrational states can be described straightforward with a SiH diatomic Morse oscillator wavefunction, this is an indication of vibrational bond localization.